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Create an instance of DecimalFormat with the required format and use its format() method to format the double value. See the DecimalFormat javadoc for details on specifying format.

double d = 1.23456789;

// Use 2 decimal places

NumberFormat numberFormat =
   new DecimalFormat("#.##");

String s = numberFormat.format(d);
System.out.println(s);   // Outputs: 1.23 

written by objects \\ tags: double, format, string

Use static method Double.toString()

double d = 123.456;
String s = java.lang.Double.toString(d);

// An alternative would be to
// use the following string concatenation

String s2 = "" + d;

written by objects \\ tags: conversion, double, string

The Double class contains a number of (static) methods for converting to/from various formats. To convert to a double use static method Double.parseDouble()

String s = "123.456";
try
{
   double d = Double.parseDouble(s);
}
catch (NumberFormatException ex)
{
   // s is not a double
}

written by objects \\ tags: conversion, double, string